Modified triplets with reduced secondary spectrum

ABSTRACT

A printer lens consists of a middle negative biconcave component surrounded by two positive doublets, with the lens parameters being selected to reduce secondary spectrum.

United St:

Vangraafeilanc [54] MODIFIED TRIPLETS WITH REDUCED SECONDARY SPECTRUM [72] lnventor: Wesley H. Vangraafeiland, 901 Elmgrove Road, Rochester, NY. 14650 [22] Filed: Oct. 1, 1971 [2]] Appl. No.: 185,602

[52] US. Cl. ..350/227 [51] Int. Cl. ..G02b 9/26 [58] Field of Search ..350/226, 227

[56] References Cited UNITED STATES PATENTS 2,279,384 4/1942 Altman ..350/227 [451 Sept. 26, 1972 Warmisham et al ..350/227 Tronnier ..350/226 X Primary Examiner-John K. Corbin Attorney-W. H. J. Kline et al.

[.5 7] ABSTRACT the lens parameters being selected to reduce secondary spectrum.

8 Claims, 1 Drawing Figure PATENTEDSEPZB I972 3, 694, 058

WESLEY H. VAN GRAA FEILAND INVENTOR.

BY W? WfZ- ORNEYS MODIFIED TRIPLETS WITH REDUCED SECONDARY SPECTRUM CROSS REFERENCE TO RELATED APPLICATIONS 185,630, entitled Printer Lens, filed Oct. 1, 1971, in

the name of C. J. Melech. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to lenses and in particular to modified triplets with reduced secondary spectrum which may be used in printers.

2. Description of the Prior Art Secondary spectrum is the inability of a lens, even when corrected for longitudinal chromatic aberration, to focus all wavelengths of light at the same point. In a design which improves only the monochromatic aberration corrections of an achromatized lens, secondary spectrum becomes the limiting aberration of the lens. In monochromatic prints, secondary spectrum tends to reduce the contrast of the final print, particularly in fine detail areas. In color prints, secondary spectrum is manifested as a spreading of color from dark areas into adjacent light areas, a phenomenon known as color fringing or halo.

It has been known to use modified triplets of the type having two outer positive components surrounding a middle negative component for photographic printing lenses. Many such lenses are well corrected for monochromatic and longitudinal chromatic aberration. Secondary spectrum is limited in such triplets by careful selection of the materials used in each element of the triplet. Examples of such materials may be found in US. Pat. Nos. 2,645,154 and 2,645,156.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printer lens having substantially improved secondary spectrum correction.

It is another object of the present invention to provide such a printer lens with improved secondary spectrum correction which also is well corrected for other aberrations such as axial or oblique spherical aberration coma, field curvature or astigmatism.

It is still a further object of this invention to provide such a printer lens with improved secondary spectrum correction in which the effective focal length of the lens may be varied without substantially effecting the secondary spectrum correction.

These and other objects are accomplished according to this invention by lenses constructed according to the parameters to be set forth more fully in the detailed description of the preferred embodiments presented below.

BRIEF DESCRIPTION OF THE DRAWING In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings which is a diagrammatic axial cross-section of a printer lens according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT For all purposes of describing or claiming of the invention herein, the term lens shall be used to describe the complete lens and not elements or components thereof. The long conjugate side of the lens is considered the front. In all the following examples, the lens components are numbered from front to rear with Roman numerals; the lens elements are numbered from front to rear with Arabic numerals. The indexes of refraction N for the D line of the spectrum, the Abbe numbers V, the radii of curvature R, the thicknesses T and the separations S are numbered by subscript from front to rear. Radii of curvature having centers of curvatures to the rear of the surface are considered positive; those with centers of curvature to the front of the surface are considered negative. All parameters are based upon a lens focal length of mm.

In all embodiments of the invention, as illustrated in FIG. 1, component I is a positive doublet consisting of a front positive biconvex element 1 and a rear negative biconcave element 2. Component 11 consists of a negative biconcave element 3. Component III is a rear positive biconvex doublet consisting of a front meniscus negative element 4 concave to the rear and a rear positive biconvex element 5.

Printer lenses which are well corrected for secondary spectrums may be made according to this invention by following the specifications in the examples presented below.

EXAMPLE 1 F/6.3 F= 100mm Mag. =6.561X

Thickness or Element N, V,, Radius Separation mm mm R, 31.981 2 1.51700 64.5 T,=2.l84

S 2.052 R, $2.949 3 1.65317 39.7 T, 1.920

. s, 4.848 R. 144.72 4 1.65317 39.7 T,=4.93l

EXAMPLE 2 F/5.0 F 100mm Mag. 10.370X

Radius Thickness or Element N V min Separation S, 2.103 R, =54.270 3 1.65317 39.7 'l,= 1.967

EXAMPLE 3 F/S .0 F 100mm Mag. 6.497X

Thickness or Element N N Radius Separation mm mm R, =-32.3e1 2 1.51700 64.5 T,=2.210

S, 2.076 R, 53.579 3 1.65317 39.7 T,= 1.942

S, 4.906 R, 146.44 4 1.65317 39.7 T.=4.990

EXAMPLE 4 Fl4.5 F =100mm Mag. 7.102X

Thickness or Element N,, V,, Radius Separation mm mm S, 1.932 R,=50.476 3 1.65317 39.7 1 T,=1.813

s',= 4.466 R,= 136.88 4 1.65317 39.7 T,=4.634

EXAMPLE 5 F/4.5 F 100mm Mag. 7.096X

Thickness or Element N, V,, Radius Separation mm mm S, 2.103 R,=-54.260 3 1.65317 39.7 T,= 1.973

S, 4.769 R,= 148.96 4 1.65317 39.7 T,=5.043

Examples l-S are extremely similar to each other. All of the examples have been normalized for ease of comparison so that the lens focal length is 100mm. 1n the designs as originally conceived, the parameters in each of the examples l-S were identical with the exception of radius R, of the rear surface of rear element 5 of component 111. The identical parameters may be found below in table 1. It was found that well corrected lenses were obtained with focal lengths which varied from 53.74 to 60.43mm as is shown in table 11 by varying R without substantially affecting the secondary spectrum correction.

TABLE 1 Thickness or Element N V Radius Separation mm mm S, 2.052 R, 52.949 3 1.65317 39.7 T,= 1.920

S, 4.848 R, 144.72 4 1.65317 39.7 T,=4.931

R, See Table 11 TABLE 11 Example R, F 5

mm mm EXAMPLE 6 Fl4.5 F= mm Mag.=11.188X

Thickness or Element N V Radius Separation mm mm S, 2.274 R, =51.346 3 1.65317 39.7 T,=2.640

S, 5.987 R, 482.92 4 1.65317 39.7 T,=2.614

EXAMPLE 7 F/5.0 F =100mm Mag. 9.120X

Radius Thickness or Element N,, V, mm Separation s, 1.590 R,=-38.939 5 1.65317 39.7 T,=1.911 R,= 32.308 s,= 3.608 R,= 214.87 4 1.65317 39.1 T,= 1.987

Examples 6 and 7 differ from each other and from examples 1-5 by the selection of design parameters but each is well corrected for secondary spectrum.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

1 claim:

1. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

wherein, from front to rear, the lens elements are numbered from l-5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R, to R the thicknesses are numbered from T, to T and the air spaces are numbered from S, to S 2. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

Radius Thickness or Element N,, V,, mrn Separation S, 2.103 R, =54.270 3 1.65317 39.7 T,= 1.967

S, 4.970 R,= 148.33 4 1.65317 39.7 T,=5.054

wherein, from front to rear, the lens elements are numbered from l-5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R, to R the thicknesses are numbered from T, to T, and the air spaces are numbered from S, A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

Thickness or Element N V Radius Separation mm mm wherein, from front to rear, the lens elements are numbered from l-S, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R, to R the thicknesses are numbered from T, to T, and the air spaces are numbered from S, to S 4. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

Thickness or Element N V Radius Separation mm mm s, 1.932 R, 50.476 3 1.65317 39.7 T,=1.813

S,= 4.466 R.= 136.88 4 1.65317 39.7 T, =4.634

wherein, from front to rear, the lens elements are numbered from l-5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R, to R the thicknesses are numbered from T, to T and the air spaces are numbered from S, to 8,.

5. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

Thickness or Element N, V,, Radius Separation mm mm R,= -32.a34 2 1.51100 64.5 r, 2.252

s 2.103 R,= -54.260 3 1.65311 39.1 r,-= 1.913

wherein, from front to rear, the lens elements are numbered from 1-5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R, to R,,, the thicknesses are numbered from T, to T and the air spaces are numbered from S, to S,.

6. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

Thickness or wherein, from front to rear, the lens elements are numbered from 1-5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R, to R,,, the thicknesses are numbered from T, to T and the air spaces are numbered from S, to 8,.

7. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

Thickness or Separation Radius Element N V mm R,-35.012 1 1.62005 63.5 T,=l6.7l0

n,=-21.2oo 2 1.51100 64.5 r,=2.241

s,=1.590 R.=-3a.939 3 1.65311 39.1 T,=1.9|1

R.=32.3os

s,=3.6os R.=214.a1 4 1.65311 39.1 r,=1.9111

R,=23.63o 5 1.14500 46.4 r,=1.139

wherein, from front to rear, the lens elements are numbered from l-5, th corresponding indexes of refract1on and Abbe num ers are for the D l1ne of the spectrum, the radii are numbered from R, to R the thicknesses are numbered from T, to T, and the air spaces are numbered from S,

8. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table:

Thickness or Element N V Radius Separation mm mm R, 27.655 1 1.62005 63.5 I T, 9.879

S, 2.052 R, =-52.949 3 1.65317 39.7 T,= 1.920

S, =4.848 R,= 144.72 4 1.65317 39.7 T.=4.931

wherein, from front to rear, the lens elements are numbered from l-5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R, to R the thicknesses are numbered from T, to T and the air spaces are numbered from S, and the radius of curvature R, of the rear surface of element 5 being between 34.000 and 39.000.

t i i t Po-ww omits @TA'EES Wasn't omw (5/69) v. i m .L

CERTWEQA'EE @F QUEKREQTEfiN Patent No. ,694,058 Dated October-1, 1972 Inventor) W. H. Vangraafeiland It is certified that error appears in the above-identified patent and that said Letters vPatent are hereby corrected as shown below:

Column 2, line 63 Please delete the second "R Column. 3, line 9 Please delete the second "N and substitute therefor "V Signed and sealed this 22nd day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTS C HALK Attesting-Offi'cer' Commissioner of Patehts' 

1. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Thickness or Element ND VD Radius Separation mm mm R1 27.655 1 1.62005 63.5 T1 9.879 R2 -31.981 2 1.51700 64.5 T2 2.184 R3 212.51 S1 2.052 R4 -52.949 3 1.65317 39.7 T3 1.920 R5 26.977 S2 4.848 R6 144.72 4 1.65317 39.7 T4 4.931 R7 34.469 5 1.74500 46.4 T5 5.808 R8 -63.586 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2.
 2. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Radius Thickness or Element ND VD mm Separation mm R1 28.345 1 1.62005 63.5 T1 10.126 R2 - 32.779 2 1.51700 64.5 T2 2.239 R3 217.81 S1 2.103 R4 54.270 3 1.65317 39.7 T3 1.967 R5 27.650 S2 4.970 R6 148.33 4 1.65317 39.7 T4 5.054 R7 35.330 5 1.74500 46.4 T5 5.953 R8 - 63.468 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Thickness or Element ND VD Radius Separation mm mm R1 27.984 1 1.62005 63.5 T1 9.997 R2 32.361 2 1.51700 64.5 T2 2.210 R3 215.04 S1 2.076 R4 -53.579 3 1.65317 39.7 T3 1.942 R5 27.298 S2 4.906 R6 146.44 4 1.65317 39.7 T4 4.990 R7 34.880 5 1.74500 46.4 T5 5.877 R8 63.529 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2.
 4. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Thickness or Element ND VD Radius Separation mm mm R1 25.965 1 1.62005 63.5 T1 9.302 R2 -30.171 2 1.51700 64.5 T2 2.069 R3 199.56 S1 1.932 R4 50.476 3 1.65317 39.7 T3 1.813 R5 25.392 S2 4.466 R6 136.88 4 1.65317 39.7 T4 4.634 R7 32.437 5 1.74500 46.4 T5 5.489 R8 59.838 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2.
 5. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Thickness or Element ND VD Radius Separation mm mm R1 28.256 1 1.62005 63.5 T1 10.123 R2 -32.834 2 1.51700 64.5 T2 2.252 R3 217.17 S1 2.103 R4 -54.260 3 1.65317 39.7 T3 1.973 R5 27.633 S2 4.769 R6 148.96 4 1.65317 39.7 T4 5.043 R7 35.299 5 1.74500 46.4 T5 5.973 R8 -63.712 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2.
 6. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Thickness or Element ND VD Radius Separation mm mm R1 33.041 1 1.62005 63.5 T1 11.738 R2 - 36.123 2 1.51700 64.5 T2 3.137 R3
 11588. S1 2.274 R4 51.346 3 1.65317 39.7 T3 2.640 R5 32.317 S2 5.987 R6 482.92 4 1.65317 39.7 T4 2.614 R7 32.502 51.74500 46.4 T5 7.816 R8 -55.434 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2.
 7. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Radius Thickness or Element ND VD mm Separation mm R1 35.072 1 1.62005 63.5 T1 16.710 R2 - 27.200 2 1.51700 64.5 T2 2.247 R3 185.47 S1 1.590 R4 - 38.939 3 1.65317 39.7 T3 1.911 R5 32.308 S2 3.608 R6 214.87 4 1.65317 39.7 T4 1.987 R7 23.630 5 1.74500 46.4 T5 7.139 R8 - 43.542 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2.
 8. A printer lens having a middle negative component surrounded by two positive doublets, said lens being constructed according to the following table: Thickness or Element ND VD Radius Separation mm mm R1 27.655 1 1.62005 63.5 T1 9.879 R2 -31.981 2 1.51700 64.5 T2 2.184 R3 212.51 S1 2.052 R4 -52.949 3 1.65317 39.7 T3 1.920 R5 26.977 S2 4.848 R6 144.72 4 1.65317 39.7 T4 4.931 R7 34.469 5 1.74500 46.4 T5 5.808 wherein, from front to rear, the lens elements are numbered from 1- 5, the corresponding indexes of refraction and Abbe numbers are for the D line of the spectrum, the radii are numbered from R1 to R8, the thicknesses are numbered from T1 to T5 and the air spaces are numbered from S1 to S2, and the radius of curvature R8 of the rear surface of element 5 being between -34.000 and -39.000. 